Project Summary In the near future, the majority of unilateral cochlear implant (CI) users will have usable residual acoustic hearing in the non-implanted ear (Dorman et al., 2009a). For these patients, speech understanding is best when electric (E) and acoustic (A) stimulation (S) are combined (EAS). There is, however, a great deal of variability in the amount and time course of EAS benefit. The long-term goal of the proposed research is to maximize the speech performance of EAS patients with targeted auditory training. The aim is to investigate the effects of speech training in quiet on the EAS benefit. Twenty, adult, postlingually-deafened, CI users with a conventional CI in one ear and with a hearing aid (HA) in the non-implanted ear will be recruited. All subjects will be tested in baseline measures including speech recognition performance in quiet and in noise, and subjective hearing assessments (baseline). After completing measurement of baseline performance, the subjects will be equally divided into two groups: 1) training with E-only stimulation via CI and 2) training with EAS via HA+CI. Phonemic contrast training in quiet will be performed at home with minimal supervision using custom software loaded onto subjects' home computers. Subjects will be trained for a half-hour per day/5 days per week for 1 month. After training is completed, baseline performance will be re-measured again (post-training) to see any effects of targeted training. One month after training is stopped, baseline performance will be re- measured again (follow-up) to see whether any training benefits were retained. The proposed experiment will provide insight into the effects of speech training in EAS patients for a variety of listening conditions. More importantly, the training may directly benefit EAS patients who participate in the experiment and provide guidance for appropriate auditory rehabilitation techniques for all EAS patients.